NATURAL HISTORY SOCIETY OF GLASGOW. 165 



Mr John Young, F.G.S., exhibited several large specimens of 

 Limnaea stagnalis, obtained during the summer of the present year 

 at Possil marsh, and stated that, so far as he was aware, this shell 

 had not hitherto been recorded from any locality in the West of 

 Scotland. He believed it must have been introduced into the 

 marsh from some English or Irish locality since the summer of 

 1867, in which year a diligent search had been made at Possil 

 for fresh-water shells, without leading to the discovery of this 

 species. In the present year, however, it had been found over a 

 great area of the marsh, and Possil is likely therefore to become 

 a station for this fine shell so long as it remains undrained. The 

 specimens exhibited, which were of a considerable size, had spawned 

 freely in ?n aquarium where they had been placed, and the young 

 shells had attained the length of quarter of an inch. 



Mr Young also exhibited some white transparent specimens 

 of Ancylus lacustris, which had been bred in the aquarium from 

 the incrusted and dark-coloured specimens found in Possil marsh, 

 and stated his belief that the variety of this shell named alhida, as 

 well as other colourless and transparent varieties, is produced by 

 the condition of the water in which the molluscs are reared; all 

 shells being more or less covered with a black incrustation where 

 decaying vegetable matter is abundant. 



Professor Young then made some remarks on the structure of 

 the wing-bones of birds in relation to their use in flight. 



October 31st, 1871. 



Professor Young, M.D., F.G.S., President, in the chair. 



Messrs Donald W. Dickson and Arthur Okell were elected resi- 

 dent members. 



Before proceeding with the business of the meeting, Dr Young 

 adverted to the appearance during the past month of two impor- 

 tant contributions to the scientific literature of the West of Scot- 

 land by members of the Society, viz.: — Messrs Young and Arm- 

 strong's work on Carboniferous fossils, and Mr Eobert Gray's 

 volume on the ''Birds of the West of Scotland, including the 

 Outer Hebrides," both of which reflected much credit upon the 



authors, and also upon the Society as a body. 

 VOL. II. M 



